This invention relates to blow molded plastic containers, and more particularly, though not exclusively, to closures for blow molded hot fill plastic containers.
Material memory, as used herein, is the propensity of materials, particularly plastics (especially polyesters, e.g. PET), to return to a previous shape or size upon the relief of internal stresses, produced, for example, by molecular orientation when blow molding an article from a preform, the relief usually being provided by the application of energy to heat the material to a stress relieving temperature.
Bottles or containers made from polyesters, usually polyethylene terephthalate (PET) or other plastics, are well known, and provide a lighter, more economical, and typically stronger alternative to older, more traditional glass or metal containers.
PET containers are typically manufactured using plastic preforms in conjunction with a blow molding process. Such containers come in all shapes and sizes, may be wide-mouthed or narrow-mouthed, and are provided with numerous types of closures including, for example, screw-on closures and snap-on closures. Frequently, the containers"" necks will be provided with complementary attachment means (neck finishes) for facilitating the attachment of the respective types of closures.
Wide mouth blow molded containers are often outfitted with screw-thread neck finishes via an injection stretch blow mold process, the neck finish being made during the initial injection molding process of the preform. One problem with wide mouth neck finishes and closures is that extra manufacturing steps may be necessary to ensure the neck area is as strong as the rest of the container. This is because during the stretch blow molding process the body of the container is biaxially oriented (thus increasing its relative strength), while the neck area is not (because the injection molding process does not significantly orient the plastic). Intermediate heat treatment steps and the like may be necessary to ensure proper strength throughout the container.
Alternatively, wide mouth containers may be provided with a simpler neck finish once the blow molding process is completed by mechanically manipulating the neck area. For example, the neck rim may be formed into a circumferential, rolled lip, onto which a complementary closure is simply snapped into place. Such a closure, though, may not always provide an adequate seal, and it may not be desirable to have such a wide product dispensing opening in the container once the closure is removed.
Wherefore, it is an object of the present invention to overcome the aforementioned problems and drawbacks associated with the prior art designs by providing a novel and advantageous closure for wide mouth, plastic blow molded containers.
Another object of the invention is to provide a method for closing wide mouth containers which allows for a variety of closure types.
Another object of the present invention is to provide a wide mouth blow molded container having a permanently secured wide mouth closure.
Yet another object of the invention is to provide a simpler and more economic method of closing and producing wide mouth containers having uniform or near uniform container strength without the necessity of many additional manufacturing steps.
Another object of the present invention is to provide a wide mouth blow molded container wherein the closure may be a compound closure having multiple and/or alternative closure parts.
Yet another object of the invention is to provide a wide mouth container closure having an enhanced seal, and the potential to provide numerous types of seals.
The present invention provides, in combination, a container and closure comprising: a container defining an opening and having at least one portion with a material memory; and a closure insert defining a closure periphery, the closure insert being secured in the container by material shrinkage produced by relief of stresses in the material memory container portion to conform that portion to the closure periphery.
The present invention also provides a method of closing a container comprising the steps of: providing a container defining an opening and having at least one portion having a material memory; providing a closure defining a closure periphery; positioning the closure in the container with at least a portion of the closure periphery being proximate the material memory portion; and heating the material memory portion sufficient to cause the material memory portion to shrink and thereby engage and conform to the closure periphery.
The present invention also provides a method of manufacturing a container having a closure, the method comprising the steps of: blow molding a container comprising a body and an accommodation element from a thermoplastic material, the accommodation element comprising an annular flange having a horizontal, radially extending portion and a vertical, axially oriented portion extending upwards from an edge thereof, the horizontal and vertical portions defining an inwardly facing, circumferential corner, and the material of the body and at least a portion of the accommodation element proximate the body being biaxially oriented via the blow molding process; trimming and removing a portion of the accommodation element above the vertical portion of the annular flange in order to provide a container opening defined by the annular flange; providing a closure insert having a closure periphery; positioning the closure insert across the container opening such that at least a portion of the closure periphery rests in the corner of the annular flange; and heating the annular flange sufficient to shrink the annular flange to engage and conform to the portion of the closure periphery resting in the corner of the annular flange.
The present invention also provides a method of closing a container comprising the steps of: providing a container having at least one generally planar portion, the container defining an opening, and the container having at least one flap integral with the at least one generally planar portion, the at least one flap extending beyond the opening, and the container having at least one portion having a longitudinal material memory, the at least one material memory portion being proximate a junction between the at least one flap and the at least one generally planar portion; and heating the material memory portion sufficient to cause the material memory portion to longitudinally contract, the at least one flap thereby generally folding over to at least partially cover the opening.
The present invention discloses a blow molded, biaxially oriented plastic canister or container having a generally cylindrical body, a bottom, and a tapering upper portion, which terminates at a wide mouth or opening surrounded by a radially outwardly directed annular flange. The annular flange includes a horizontal, disc-like portion and a vertical, cylindrical portion extending up from the horizontal portion. A generally disc-shaped closure insert having a circumferential rim and a dispensing outlet is placed across the opening such that the closure rim is generally fitted into a corner formed by the horizontal and vertical portions of the annular flange.
Heat or some other form of radiant energy is applied to the entirety of the annular flange, which, having been at least radially or circumferentially oriented during the blow molding process, shrinks in response to tightly conform to and engage the closure rim, forming a circumferential seal. The dispensing outlet may be provided with an outlet closure, such as a screw cap or the like, depending on the configuration of the provided dispensing outlet. Also, a sealing gasket or the like may be disposed between the annular flange and the closure rim before the heat is applied in order to form an enhanced seal. Furthermore, mechanical devices may be used to shape the flange during or after heating to further enhance the rim-flange seal or to provide additional sealing configurations.